Mysidium (Mysidium) cubanense Băcescu & Ortiz, 1984

Wittmann, Karl J. & Wirtz, Peter, 2019, Revision of the amphiamerican genus Mysidium Dana, 1852 (Crustacea: Mysida: Mysidae), with descriptions of two new species and the establishment of two new subgenera, European Journal of Taxonomy 495, pp. 1-48 : 12-14

Mysidium (Mysidium) cubanense Băcescu & Ortiz, 1984

Fig. 3

Mysidium cubanense Băcescu & Ortiz, 1984: 18 –20, fig. 2A–K.

Mysidium cubanense – Harrison & Bowman 1987: 678 (in comparison). — Ortiz & Lalana 1988: 14 (in list); 1997: 187; 2018: 67. — Băcescu 1991: 3 –6. — Escobar-Briones & Soto 1991: table 1. — Ortiz 2001: 100 (in list). — Ortiz et al. 2006: 3; 2017 a: 113; 2017 b: 72–74. — Petrescu & Wittmann 2009: 54. — Price & Heard 2009: 938 (in list).

Mysidium cubanensis — Harrison & Bowman 1987: 674, 678 (gender inconsistency).

Type material examined

Holotype

CUBA • adult ♂, partly dissected, bl 4.5 mm; in front of Marine Research Center , Habana, at the entrance of a small underwater cave; 23.1334° N, 82.3334° W; 13 m; 13 May 1983; Manolo Ortiz leg.; Mihai Băcescu det.; MINGA 49346 /601a.

Other material examined

CURAÇAO • 104 ♀♀ ad. bl 3.9–5.5 mm, 70 ♂♂ ad. bl 3.4–5.2 mm, 32 subad.; # C 3; NHMW 26478 • 2 ♀♀ ad. bl 3.6–4.1 mm; # C 4; ZMH K-55257 • 383 ♀♀ ad. bl 4.2–5.8 mm, 96 ♂♂ ad. bl 3.1–5.9 mm, 15 subad.; # C 5; MINGA MYS 432 • 15 ♀♀ ad. bl 3.7–5.8 mm, 3 ♂♂ ad. bl 3.0– 4.7 mm, 10 subad.; # C 8; ZMH K-55259 .

BONAIRE • 20 ♀♀ ad. bl 3.2–4.4 mm, 5 ♂♂ ad. bl 3.3–4.0 mm, 10 subad.; # B 11; MINGA MYS 438 .

Type locality

Miramar, La Habana, Cuba ( Băcescu & Ortiz 1984), 23.1334° N, 82.3334° W.

Revised definition

All features diagnosed above for genus and subgenus Mysidium Dana, 1852 . Cornea large, globose to ellipsoidal in lateral view, calotte-shaped to crescent-like in dorsal view, with ‘diameter’ 2.6–4.1 times as long as terminal segment of antennular trunk. Eyestalks smooth. Rostrum (sub)triangular, apically bluntly pointed to well rounded, not extending beyond basis of eyestalks. Antero-lateral edges of carapace rounded. Only males with anterior margin of antennular trunk dorsally with rounded, shield-like, mediodistal extension ( Fig. 3A–B ); longitudinal series of 4–6 setae extending all over this extension plus a short proximal stretch. The largest seta 0.2–0.4 times extension length. Appendix masculina bilobate, all along inner margins fringed by large setae; its length 1.1–2.3 times terminal segment of antennular trunk. Length of antennal scale 4–6 times maximum width; scale reaching beyond antennular trunk. Median segment of mandibular palp with setae on both margins. Large, about evenly rounded hump on outer face of distal segment of maxillula. Carpopropodus with two segments in thoracic endopods 1–2, 8, versus three segments in endopods 3–7. Basal segment occupies half total length of carpopropodus of endopod 3. Pleopod 1 bilobate in both sexes. Sympod of male pleopod 4 with endite reduced to weak medial hump or missing. Basal segment of exopod occupies 54–61% total length. Endopod reduced to lobe with 14–18% sympod length; apically with one long seta and more proximally additional 4–6 shorter, barbed setae. Endopod of uropods 0.6–0.8 times as long as exopod. Telson subrectangular to trapezoid; length 1.6–2.1 times maximum width near basis; its lateral margins slightly concave to almost straight; latero-terminal corners rounded; terminal margin traverse to convex. Proximal 48–73% of lateral margins smooth, distal portion of each margin with dense, continuous series of 7–16 acute spines. This series extending up to the rounded, latero-terminal corner. Terminal margin lined by 12–20 densely set, apically blunt or weakly pointed laminae.

Descriptive notes

Adult females of present material with 3.2–5.8 mm (n = 524) body length, males 3.0– 5.9 mm (n = 174). Antennular trunk extends 0–20% its length beyond (artificially aligned) eyes ( Fig. 3A ). Antennal scale 1.1–1.4 times as long as trunk. Sympod of antenna produced into spiniform extension on outer distal corner. Thoracic endopod 8 (when stretched) reaching backwards at most to end of pleonite 4 and forwards to mandibles; its carpopropodus 60–83% as long as merus or 26–45% times as long as telson. Pleonites 1–5 are 0.5–0.6, 0.5–0.6, 0.5–0.7, 0.5–0.7 or 0.5–0.7 times as long as pleonite 6, respectively. Sizes increase from pleopods 1 to 4, while pleopod 5 ranges between 1 and 2 in both sexes; amplitude of this variation much stronger in males than females. Pleopods 1 and 3 stouter compared to remaining pleopods. Pleopods 2–5 of females and 2, 5 of males are essentially rod-like. Pleopods 1–3 with a ventrolaterally directed fan of plumose setae in both sexes. Setae forming the fan of pleopod 1 ( Fig. 3D ) larger than those of pleopods 2–5 in females and 2, 3, 5 in males. Male pleopod 4 ( Fig. 3F ) reaching at most to distal 4/5 of pleonite 6; its subapical seta up to end of telson. Endopod with apical seta 1.4–2.8 times endopod length. Sympod with field of scales on its weak medial hump, or in analogous position upon missing hump. Scutellum paracaudale triangular with acute apex; upper margin convex or S-shaped, lower margin straight to slightly convex or S-shaped. Uropodal endopod 1.1 times, exopod 1.4–1.6 times as long as pleonite 6. Exopod extends 0.3–0.4 times its length beyond endopod, or 0.4–0.6 times its length beyond telson; endopod 0.3–0.4 times its length beyond telson. Telson ( Fig. 3G ) length 0.5– 0.6 times as long as uropodal exopod, 0.6–0.7 times endopod and 0.7–0.8 times pleonite 6. Statoliths composed of fluorite. Structure of foregut and nauplioid larvae essentially as in M. triangulare sp. nov. ( Fig. 8A–F, M–N ).

Distribution

Euhaline coastal waters in the Gulf of Mexico, Bahamas, Cuba, Jamaica, Caribbean ( Ortiz et al. 2017b). The present records are the first for Bonaire and Curaçao, thus extending the known latitudinal range southward to 12–23° N. Most samples are from swarms between corals.

Figures

Fig. 3. Mysidium cubanense Băcescu & Ortiz, 1984, from Cuba (A), Curaçao (B–F) and Bonaire (G). A. Holotype, ♂, 5.1 mm body length. B–F. Non-type, ♂, 5.0 mm. G. Non-type, ♂, 4.0 mm. A. Cephalic region, right antennula and setae of antennal scale omitted. B. Mediodistal extension of left antennular trunk, dorsal view. C. Third thoracic endopod, rostral view. D–E. Pleopods 1 and 3, rostral view. F. Pleopod 4, caudal view. G. Telson. Sample affiliation: Cuba - type locality (A); Curaçao #C3 (B–F); Bonaire #B11 (G).

Fig. 8. Mysidium triangulare Wittmann sp. nov., from Curaçao, paratypes. A–F. ♀, 5.9 mm body length. G, J. ♀, 5.1 mm. H, K–L. ♂, 5.5 mm. A. Foregut; dorsal wall omitted. B–F. Details of panel (A) showing modified spines. G. Basal half of thoracopod 7 with right oostegite, lateral view. H, J. Variants of scutellum paracaudale, lateral view. K. Uropods, ventral view; setae omitted. L. Telson. M. Nauplioid larva at substage N2, lateral view. N. Detail showing tip of abdomen in another nauplioid specimen.